Why does my RO system raise PH from 7.0 to 9.5??

I've been using the same RO system by Watts (a very good one, filters are fresh). And in the are we just moved to it raises the PH from 6.9 (tap water) to 9.5 (after RO). Ppm only drops from 60 to 50ppm.

Any ideas why it's raising the Ph so much? Also is 9.5 Ph safe to drink?

replace the filters

water is good to drink up to 500 ppm dont think ph matters much. just for plants they need 5.5-6.5ph 5.8 is the best if u didnt kno